Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session C25: Multiphase Flows: Computational Methods II |
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Chair: Elias Balaras, George Washington University Room: 607 |
Sunday, November 24, 2019 8:00AM - 8:13AM |
C25.00001: A Numerical Formulation to Study Interactions Between Fluids and Deforming Solid Jiazhen Qiao, Amir Riaz, Akash Dhruv, Elias Balaras In the present work, level set formulations are used to track solid-fluid interface as well as to track a dynamic grid which captures solid deformation. The solid is assumed to be viscoelastic and a unified framework of equation of motion is used to solve for both fluid and solid dynamics. Fluid-Structure Interaction is accounted for by using an external body force term to enforce no-slip boundary condition at the interface and an elastic stress term to impose elastic stress boundary condition at the interface. The elastic stress term is implemented through a pressure jump which corrects the pressure distribution as well as the velocity field in the computational domain as a result of the presence of the elastic solid. The proposed method has an advantage of robust implementation in three dimensions and has the potential of incorporating different viscoelastic models to account for various material properties. [Preview Abstract] |
Sunday, November 24, 2019 8:13AM - 8:26AM |
C25.00002: Advancements to a Dual-Scale approach for Simulating Turbulent Phase Interface Interactions Dominic Kedelty, Marcus Herrmann, Thomas Ziegenhein Direct Numerical Simulation remains an expensive task for atomization simulations. To decrease the burden of DNS, a dual-scale modeling approach (Gorokhovski and Herrmann, 2008) that describes turbulent phase interface dynamics in a Large Eddy Simulation spatial filtering context is proposed. Spatial filtering of the equations of fluid motion introduce several sub-filter terms that require modeling. Instead of developing individual closure models for the interface associated terms, the dual-scale approach uses an exact closure by explicitly filtering a fully resolved realization of the phase interface. This resolved realization is maintained using a Refined Local Surface Grid approach (Herrmann, 2008) employing an unsplit geometric Volume-of-Fluid method (Owkes and Desjardins, 2014). Advection of the phase interface on this DNS scale requires a reconstruction of the fully resolved interface velocity. In this work, results from the dual-scale LES model employing sub-filter turbulent eddy reconstruction by combined approximate deconvolution and non-linear spectral enrichment (Bassenne et al. 2019) and sub-filter surface tension model (Herrmann 2013) are compared to DNS results for a phase interface in a homogeneous isotropic turbulent flow at two different Weber numbers. [Preview Abstract] |
Sunday, November 24, 2019 8:26AM - 8:39AM |
C25.00003: A volume of fluid method for interface-resolved simulations of evaporating flows Nicol\`{o} Scapin, Pedro Costa, Luca Brandt We developed a numerical framework to study the evaporation process of a liquid in an inert gas using the volume of fluid method. The proposed methodology successfully addresses the two main challenges in performing direct numerical simulation of phase-changing flows when a whole-domain formulation is adopted: the interface-normal velocity jump and the accurate calculation of the interfacial mass-flux exchanged between the two phases. The former is handled by constructing a continuous and divergence-free liquid velocity field, which is used to compute the interface velocity, while the latter is accomplished by reconstructing a level-set function. The resulting approach is built on top of an efficient, FFT-based two-fluid Navier-Stokes solver coupled with an algebraic volume of fluid method (MTHINC), and extended with the corresponding transport equations for the vaporized liquid mass and thermal energy. The method was thoroughly tested against benchmarks of increasing complexity, which show its excellent mass conservation properties and good overall performance. [Preview Abstract] |
Sunday, November 24, 2019 8:39AM - 8:52AM |
C25.00004: Quadric interface reconstruction from volume fractions for curvature estimation Austin Han, Olivier Desjardins In this talk, we present a new method for evaluating the curvature of a captured interface in the context of volume of fluid (VOF). This method endeavors to fit a paraboloid to the interface using only volume fraction data in a neighborhood of cells. It shares strong similarities with the height-function (HF) method, which also represents the interface as a paraboloid. But because the HF method orients the paraboloid along the directions of the underlying Cartesian mesh, its accuracy deteriorates severely in cases of poorly resolved slanted interfaces. In contrast, we allow here for the paraboloid to be arbitrarily rotated and propose a method for evaluating the volume of each cell capped by the arbitrary paraboloid. We verify the performance of this approach on a range of canonical problems, paying special attention to the dependence of the error on the alignment of the interface with the mesh. Finally, we discuss the extension of this method to unstructured meshes. [Preview Abstract] |
Sunday, November 24, 2019 8:52AM - 9:05AM |
C25.00005: On algebraic TVD-VOF methods for tracking material interfaces Sergio Pirozzoli, Simone Di Giorgio, Alessandro Iafrati We revisit simple algebraic VOF methods for advection of material interfaces based of the well established TVD paradigm. We show that greatly improved representation of contact discontinuities is obtained through use of a novel CFL-dependent limiter whereby the classical TVD bounds are exceeded. Perfectly crisp numerical interfaces are obtained with very limited numerical atomization (flotsam and jetsam) as compared to previous SLIC schemes. Comparison of the algorithm with accurate geometrical VOF shows larger error at given mesh resolution, but comparable efficiency when the reduced computational cost is accounted for. [Preview Abstract] |
Sunday, November 24, 2019 9:05AM - 9:18AM |
C25.00006: Height-function method for curvature estimation on two- and three-dimensional non-uniform Cartesian grids Fabien Evrard, Fabian Denner, Berend van Wachem Estimating the curvature of an interface from the corresponding discrete indicator function field is known as one of the main challenges associated with the simulation of interfacial flows with surface tension. The sharpness of the discrete indicator function renders classical differenciation approaches ineffective (understand: divergent) as the mesh resolution is increased. Out of all the methods available in the literature, the height-function (HF) method is the sole example of a curvature estimation technique that converges with mesh refinement and has been shown to exhibit performances that are superior to other approaches when coupled to a multiphase flow solver. Although a second-order accurate general formulation for non-uniform Cartesian grids has been derived for the two-dimensional case, the three-dimensional HF formulas have so far been limited to uniform Cartesian grid configurations, where they correspond to classical finite difference formulas. This work presents an extension of the well-known height-function curvature estimation method to non-uniform Cartesian grids, both for the two- and three-dimensional cases. The convergence of the method is studied throughout its application to known analytical surfaces, and ways to improve its order are discussed. [Preview Abstract] |
Sunday, November 24, 2019 9:18AM - 9:31AM |
C25.00007: A diffused-interface approach for simulating compressible multiphase flows within an adaptive mesh refinement framework Karthik Kannan, Fabian Fritz, Nico Fleischmann, Carlos Ballesteros, Marcus Herrmann A diffused-interface method for solving the compressible, multicomponent Navier-Stokes equations, i.e. the quasi-conservative five-equation model (Allaire et al., 2002) including capillary and viscous effects (Coralic and Colonius, 2014, Garrick et al., 2017) is used in conjunction with a novel, unstructured, cell-based adaptive mesh refinement (AMR) library (Ballesteros, 2019). Low dissipation, high spatial resolution is obtained by using a WENO-Z (Borges et al., 2008) discretization, while the numerical smearing of the material interface is controlled using a THINC scheme (Shyue and Xiao, 2014). This ensures higher-order while limiting the material interface width to 2-3 mesh cells. Surface tension effects are incorporated by means of a modified HLLC solver (Garrick et al., 2017). Curvature is computed using a stretched variant of the standard height function method (Cummins et al., 2005) to account for the smearing of the material interface. The use of AMR helps achieve higher mesh resolution in regions of liquid and shock discontinuities, which is crucial to compressible atomization applications. Results for test cases ranging from shock-interface interaction to liquid atomization are presented. [Preview Abstract] |
Sunday, November 24, 2019 9:31AM - 9:44AM |
C25.00008: Surface tension effects on the evolution of interfaces in multimaterial compressible flows Pedram Bigdelou, Praveen Ramaprabhu We report on the effect of surface tension on the evolution of perturbed material interfaces in compressible multimedium flows. The level set method is used to track the interface, while the real Ghost Fluid Method$^{\mathrm{1}}$ (rGFM) captures the interfacial coupling between the fluids. We implement these techniques in an in-house code IMPACT, designed for simulation of compressible flows with shocks and material interfaces. We present various test problems to address how surface tension affects the growth of perturbed interfaces driven by shocks. In particular, we examine surface tension effects on the baroclinically driven Richtmyer-Meshkov instability$^{\mathrm{2,3}}$. The 2D simulations were initialized with a sinusoidal perturbation imposed at the interface. An incident shock crosses the interface, followed by the growth of the imposed perturbation. The simulations were conducted at different values of the surface tension, and the variation in the instability growth rate was compared with recently proposed models. $^{\mathrm{1}}$Wang C.W., Liu T.G., Khoo B.C., SIAM J. Sci. Comput. 28(1) (2006) 278-302. $^{\mathrm{2}}$Richtmyer R.D., Commun. Pure Appl. Math. 13 (1960) 297-319. $^{\mathrm{3}}$Meshkov E.E., Fluid Dyn. 4 (1969) 101-104. [Preview Abstract] |
Sunday, November 24, 2019 9:44AM - 9:57AM |
C25.00009: ABSTRACT WITHDRAWN |
Sunday, November 24, 2019 9:57AM - 10:10AM |
C25.00010: Non-local surface tension model for N-phase flows Amanda Howard, Alexandre Tartakovsky We propose a nonlocal model for surface tension obtained in the form of an integral of a molecular-force-like function added to the Navier-Stokes momentum conservation equation for N-phase fluid flows. We demonstrate that our model recovers both microscale and macroscale features of multiphase flow, eliminating the need for expensive hybrid MD-NS models, and providing strong advantages for modeling multiphase flows at length scales not feasible with MD simulations. We present benchmark cases for the nonlocal model with comparisons to the level set method for N-phase flows and fluid-fluid-solid flows. Results are shown to be in agreement with analytical and previous numerical results. [Preview Abstract] |
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